In the high-speed printing field, the wire matrix printer, the thermal printer and the ink jet printer have demonstrated that both impact and non-impact printing concepts are useful in the various types of printing devices. It is of course well-known that the wire matrix printer and the ink jet printer have each utilized a composite or integral print head which includes a plurality of drivers arranged in a manner to be supported and carried as a unit and caused to be moved or driven in a lateral or transverse direction in a reciprocating or back-and-forth motion across the printer.
In the case of the ink jet printer, the print head may be a multiple nozzle type with the nozzles aligned in a vertical line and with the ink supply elements for the individual nozzles arranged in a circular or other manner in order to achieve a compact unit. However, there are various applications where the use of a multiple nozzle print head is too expensive for the particular printing concept.
As an alternative to the multiple-nozzle type print head and in the case of certain recording devices, a plurality of equally-spaced single print heads are caused to be moved in back-and-forth manner to print lines of dots in making up the lines of characters. One such device is shown and described in U.S. Pat. No. 3, 789,969 issued to R. Howard et al on Feb. 5, 1974. One of the problems encountered in the use of such equally spaced print heads which receive ink from a common ink supply is that of maintaining an even flow of ink to each of such print heads at all times throughout printer operation in the back-and-forth movement of the print heads or in a bi-directional printing manner. In a bi-directional printer, that is, one that prints in both directions of travel or movement of the print head, there are times when the printing is continued to the ends of the lines and the ink must be immediately available at the nozzle for printing in a return direction. However, at the end of each line of dots in the case of the equally spaced head ink jet printer, the sudden change in direction of the print heads creates deceleration forces and acceleration forces which forces act upon the ink in the print heads and which forces lead to oscillations in the nozzles and, under certain conditions, to air bubbles and interruptions or intermissions in the flow of ink to the nozzles of the print heads.
Representative prior art in ink jet recording devices of the type previously mentioned includes German Pat. No. 2,539,983, wherein the ink supply to the printing elements occurs through a hose-shaped flexible line connected with an ink container being secured in position. The known devices may be susceptible to high accelerations upon reversal of the printing elements and the disadvantage of such high reversal forces and irregularities or interruptions in the flow of ink to the print head may lead to improper functioning or failure of the printing elements.